Liquid operated electric control device



Aug. 22, 1944. w. KOEPPE ET AL 2,356,593

LIQUID OPERATED ELECTRIC CONTROL DEVICE Filed April 24, 1940 Patented Aug. 22, 1944 LIQUID OPERATED ELECTRIC CONTROL DEVICE Walter Koeppe,

Berlin-Spandau,

and Gustav Kodal, Berlin-Siemensstadt, Germany; vested in the Alien Property Custodian Application April 24, 1940, Serial No. 331,408 In Germany March 22, 1939 (Cl. 7S-304) 14 Claims.

This invention relates to a liquid operated electric control device particularly adapted to measure or tele-indicate liquid levels as, for instance, to indicate the residual amount of 4liquid contained in an airplane tank.

To indicate liquid levels, and particularly to tele-indicate liquid levels, floats have hitherto been employed which depending upon their posil By the electric control device according to the l invention it is possible to measure the liquid level in a particularly simple and reliable manner. The novel liquid operated electric control device for measuring liquid levels is characterized by the fact that the surface tension of the liquid serves to operate the electric control device. The electric control device according to the invention consists of at least two parts having surfaces which are movable with respect toveach other and which are so arranged that they change their position with respect to each other under the action of the surface tension of the liquid, thereby influencing an electric circuit. The two parts may consist, for instance, of a stationary part and a sheet of flexible metal foil. In this instance the metal foil comes into engagement with the surface of the stationary part under the action of the surface tension of the liquid when the parts emerge from the liquid. Of course, it is also possible to design both parts so as to be movable with respect to each other; as, for example, in the form of foils or sets of foils which when immersed in the liquid do not touch each other, whereas when they emerge from the liquid they come into engagement under the action of the surface tension of the liquid adhering to the same.

Finally, it is also possible according to the invention to cause the control device to act as a servomotor, i. e., by causing the one part when taking measurements to be set in motion, preferably in rotation. I f this part is, for instance, designed as a revolving cylinder and the other part as a ribbon-shaped foil loosely surrounding wholly or in part the cylinder, this foil will not adhere to the cylinder when immersed in the liquid, whereas it does when it emerges from the liquid, thus producing in the tangential direction of the revolving cylinder a pulling force on one part secured to the foil.

In some cases it may be preferable to provide the novei control device with a further stationary part with respect to which at least one of the other two parts movable with respect toy each other changes its position upon actuation of the control device, thereby influencing the abovementioned electric circuit or at the same time a further electric circuit. In this case this part must, however, be so designed that no appreciable effect of the surface tension occurs between Ithat part and the part movable with respect thereto. Such a control device may as hereinafter described serve, for instance, as a multiple-way switch.

Here the two parts movable with respect to each other, i. e. foil and surface, come into engagement with each other in the case of wetting liquids when emerging from the liquid, whereas if nonwetting liquids are employed the parts are in engagement with each other in the liquid and come out of engagement when they emerge from the liquid.

When using wetting liquids the parts of ocontrol device not immersed in the liquid remain in contact with each other till the liquid adherlng thereto evaporates. To prevent a subsequent separation of the parts a protection against evaporation may be provided according to the invention which supplies fresh liquid to the control device upon the evaporation of the liquid adhering to the control device not in contact with the liquid. Such a protection against evaporation may be carried out in different ways; for instance, by using a hygroscopic material for one part of the control device, a portion of the material being always in contact with the liquid, or by arranging one or more grooves in one part of the control device whose ends are immersed in the liquid and in which the liquid rises by reason of the capillary effect or also by using a wick which brings the control device into contact with the liquid.

The control device may be caused to act in various ways on the electric circuit of which it forms, as a rule, one part. Thus, it is possible to design the control device in such a manner that when actuated it closes an electric contact. In this case one or both of the parts movable with respect to each other may be designed in the form of contacts or one part may actuate a contact by utilizing the effect of the control device operating as a servomotor. Furthermore, the control device may be employed to vary the capacity of a condenser, in which case the parts movable with respect to each other may serve as coatings for the condenser. In this case by actuating the control device sudden changes in capacity are attained which may be measured with the aid of relatively simple means.

Finally. by the use of the control device it is also possible to vary the value of an inductance, for instance, by the fact that the movable part is made of magnetic material and is so arranged in relation to the coil that changes in the position of the movable part bring about changes in the inductance.

Such a control device may be used for many purposes. As already mentioned it may be employed to indicate a liquid level upon the attainment of a predetermined height or to cause a signal to be transmitted upon the attainment of a predetermined height. Thus, for instance, in the event that the residual amount of liquid contained in an airplane tank is to be indicated, the control device may be installed on the bottom or" the tank to be supervised, and is actuated as soon as the liquid level lowers below a predetermined height. The control device may also be employed to indicate a predetermined maximum value of the liquid level.

By arranging only two control devices closely one above the other it is possible to regulate in a simple manner the liquid level to a constant value, i. e. by interrupting or reducing the flow of liquid upon the actuation of the upper control device or by initiating or increasing the flow o1' liquid upon the actuation of the lower control device.

Two or more control devices according to the invention arranged one above the other' may serve as a liquid level indicator and it is possible to easily carry out remote measurements with the aid of the same. However, their use is not limited to the indication or remote measurement of liquid levels, such as the depth of a river or the liquid level in a tank, but they may be used to meaenre other conditions, such as temperature, pressure or the like.

In principle it is immaterial whether the liquid operating the control device is the same or differs from that to be supervised or controlled. In many cases it is'preferable to use as the operating liquid another liquid than that whose level is to be supervised; for instance, when measuring the depth of a river, since the control devices are ex-v posed to a contamination by the foreign substances contained in the water. In this case a liquid is employed which avoids the above drawbacks and which does not intermix with the liquid whose level is to be supervised. However, as a rule, all kinds of liquids may be employed irrespective of whether they are conductive or nonconductive. In the dissociating liquids care should only be taken to see that the current carrying parts placed in the liquid conduct only alternating current and no direct current.

The control device may be employed for purposes other than the above mentioned, i'. e., for the indication and the remote measurement of the dew point, since it operates at the moment at .which its movable parts are wet by the dew.

In the drawing whichshows diagrammatically several embodimentsl of my invention:v

Fig. l is a view of'one'embodiment'of the in.

vention;

Fig, 2 is a view similar to Fig. 1 showing another ernbodiment of the invention;

Fig. 3 is a perspective view oi' another embodiment of the invention;

Fig. 4 is a wiring diagram showing some of the elements schematically of an embodiment of the invention similar to that of Fig. 3;

Fig. 5 is a partially schematic view of another embodiment of the invention;

Figs. 6 and 7 are schematic showings of two similar embodiments of the invention used to measure liquid level and gas pressure respectively;

Fig. 8 is a schematic showing of an embodiment of the invention;

Fig. 9 is a schematic showing of another embodiment of the invention, and

Fig. 10 shows a. modification of the structure of Fig. 3 wherein in place of electrical contacts a, variable inductance is shown.

The electric control device as shown in Fig. 1 is provided with two sets of foils I and 2 movable with respect 'to each other, electrically insulated from one another by an insulating piece 3 and pressed together by a bolt l and a clamping piece 5, 6 and 1 are connections for the sets of foils.

If such a. control device emerges from the liquid, in which case the liquid level is to be considered as being parallel to the plane of the drawing, the sets of foils come into engagement with one another, thereby influencing an electric circuit connected to the connections s and 1, In this case the two inner foils may serve as contacts, or as coatings of a condenser provided that as thin an insulating layer as possible is arranged on one or both foils.

In Fig. 2 is shown a top view of the control device consisting of two control elements arranged symmetrically with respect to the axis A-B within the ring 8. Each control element is provided with a bent stationary surface 9 forming one of the parts movable with respect to each other and to which a metal foil I0 which is somewhat more bent is insulatedly secured by means of a screw with a nut II and a clamping piece I2. The less bent stationary surface is provided with metal coatings I3 connected to one pole of the electric circuit in which is inserted the control device, whereas the other pole is connected to the metal foil. These coatings may as mentioned above serve as contacts or as the plates of a condenser.

Fig. 3 is a perspective view of a similarly designed control device. Here the less bent stationary surface is formed by the curved portion of a molded piece consisting of insulating material. I0 denotes the metal foil, Il and I2 the parts serving to secure it to the molded piece Il, I3 are the metal coatings arranged on the curved portion of the molded piece I4.

This control device differs from that shown in Fig. 2 only in certain constructional details and is so designed as to form an essential part of a liquid level indicator, such as shown, for instance, in Fig. 4 which is a lateral view thereof. In this case the molded piece H is extended by such an amount that the desired number of control devices may be arranged on the extended curved portion thereof. In this case, the metal foils I0 of the control devices may be secured by means of a. through clamping bar I2 so that the construction of such a liquid level indicator is very simple.` The metal coatings on the molded piece Il are'denoted by the numeral I3 and II designates the screws for fastening the clamping bar I2.

To attainan effective protection againstevaporation, the curvedportionl of t'hefmolded pieceis provided asshown in Fig. 'iwithnarrow. grooves' 1 arranged at 'beth sides croie cleiiipiiigber 'and serving tokeepf'the'control devices continuously in a ino' t` ,state 'when not'immerse'd in the liquid. c'

The parts;A iia simulate, ofy percus Lmeteriitif sc f tnetthe moisture may reeciitiiesiirfaces jtneeeer and lying "abovethe `liquid 'levellj It short .Cirduited sov that'4 in Wheatstojnebridge c iy arefeffefctivewhichare devices immersed in ,c the y H liquid. 'The'iristniment 23 inserted ""in' the bridge a bridge j' "connectionvk indicate die",iiciuii1@v y lviromeFigfli, the refs''ist'ances` "i: l1 sind lsljnotgco'rinected;te theccntrdldevicejs areaiways 'the' 'branch of "fthe" f theiresistances j I9r to 22` connected tofthe" control di'ee'eiieii sur always ft2 efiecta ,deflection whoser magnitude fis-a measure fcr the heightA .citheliquid levclf! Another embodiment cordlng rtofthe' invention r Fig. 15. 4 2`4jis afrcd'l'rot'atingiiji trief'direction as indicatedy by the arrow; Around'theV rod isV ar" rangedy a foil v25 one end ofjwhi'ch'isi'ree and f the',v other. end thereof` isqseoured tothe contact arm. `2li pivotally rriounted as r indicated at 11'." I

et in rotation. If in` this'casefthe4 `control device is notfi'mmersed in the'li'eiiid the fcii" will nrmlyj intheeventofa ,y l e Y between the `foil and the rod` so that the contact er, the .m'i'cvaloie` arm ,2B isiiougnt inici en:

y o adhere' to the4 rodl wettingfliquid"being present gagementlwith the counter'I contact." f If', however, f

thefcontrol device' cisfgirnniersedffilnI the: liquid `the: contacts are'out ofv engagement with onefanoth'er'. f It. is, of course.. also possible to causey theijo'di` tc.v rotate continuously se that `the vecintacts -ci thejccntr'cl device which lie above the :liquid levela'ie alwayfsfcl'osed." However, it isialsopossibleif single measurements are to' be Lcarried outat `spaced intervals towcauselthe rod to` rotate.` thatfat the interval between two' momentarily S9 measurements'all contacts In vsome` cases.' particularly are open. l Y f when measuring f desirable as"v already mentioned above' tocause the liquid whosev level ls'to bein'dicated :lotto act directly on .the control device. lIn this7 case,l an arrangement mayQbe employed as shown diagrammatically yin Fig. 6. 29 indicates, for instance, the iluctuating level of a river. 30 dcnotes a vessel with communicating tubes immersed in the river. In the longer tube is placed a liquid level indicator 3| consisting of the control devices according to the invention and surrounded by a lighter liquid 32 which preferably does not mix with the river water.

A similar arrangement` may be employed if a different physical magnitude, for instance, the pressure of a gas in the chamber 33 of Fig. 'l is to be measured. By means of the arrangement shown in Fig. 7 the super-atmospheric pressure of this gas is measured. One of the communieating tubes S4 o! the control device a vessel in which is arranged.

35 immersed in Athe liquid I8 control device is submerged `in the concave faceof` the extends within the space as and is sealed et the point'where 'it enters the vessel. The operation of this?` arrangement issimilar tothe operation require any furtheryexplainationf.

of the arrangement. shown in Fi8.'6 and `will not y e i 1f the .-Iliquid rf levelv in ienkswiicse ypceiilc'n changes is tobe measured,1f1'aulty 7measurenlents may result if only one level indicator is employed.

To avoidsuch' faultymeasurementa 'two or more controlfdevi'ce's or liquid level'y indicators are provided "accordingl 4tov the invention, `such as,y Vfor y instance, is'Tsch'ematicall'y"` shown in-frig` 8 for four 'liquidlv level vindicators yT31.'

indicators' are electric-ally connected fin vparallel relation:`v` andi'they vareso l`arranged that. upon filuctua'tioris of the liquid level as many control devices of *oneliquid level indicator are, Yfor. in-v stance,`v yclosed* ascontrol devices are opened on theiothrtvvo indicators. AInfthis:mannerthe indication oitheiiquid level withinthe' tanlr IB lis independent of its position.' lf; 'f cribed above, thecontrol device Asfalready des according to the invention may also be provided with "a furtherstationary part vwith respect toV which" the `'position for instance, of the metal foilflU (Fig. 2)'*varies upon the operation of the control deviceV yand whi'ch mayfserve,` tor instance. as amultipleewayswitch! -Such a control device is schematically shawn'i1'if1='ii i;'.^9.,asV denotes the stationery vsurfaceagainst which the ffcil 4o is `pressed under the surface tension when the con troly devicefe'merges" from theliquid, the surface :is andvtheffcii ao'being electrically insulated from each other by an insulation Il. When the the effectV of the surface tension ceases and the ends of thefoil come'y then into engagement ywith the other stationary p oi' resilient material and being tnsioned against it isH essential that'v lthe party, In this case the surface ofthe partl`2 which the '.ioil engages be small with respect tothe surface ofthe part as cn which thev rfcil isl nr'mi'yhelciby-the surface. tension, sincev otherwise it'may happenv that- ;,th fou' mlf the surface ten'si vThe" 'contr 'l device'operates asv amultiplway 39.40 and/42 areconnectedetov'the rconductors 43 tollfHowever, the conductorsl 'and'll only may be connected; or the :part I2 and/or the part 39 may be electricallyl subdividedand additional conductorslia'nd 41 maybe provided as'isvshown by the` dotted lines `in Fig.y 9'.

This control device neednot, ofcourse, be

of the outer portions of the flexible foil which'is also of magnetic material.

What is claimed is:

1. An electrical control device comprising two parts one of which is responsive to the influence of surface tension so that the parts are movable relative to each other under thev influence of the surface tension of a liquid, and means including said parts for altering an electrical circuit rel"parts insulated sponsive to relative movement thereof. j `2. An electrical control device comprising two from each other and movable with respect to each other in response tothe In athis case r the in a wetting liquid f arte, the 'foil being made adheres tothe part rlowing tolrr maybe employed to vary 'an action of surface tension so that the two parts are separated when the device is immersed in a liquid which wets the parts and which are brought together by the surface tension of the liquid when the Parts are no longer completely immersed therein, said parts being of conducting material.

3. An electrical control device comprising two parts insulated from each other and adapted for inclusion in an electrical circuit, said parts having surfaces acted on by the surface tension of a liquid to effect relative movement of said parts to control said circuit.

4. An electrical control device comprising two parts insulated from each other and adapted for inclusion in an electrical circuit, said parts having surfaces acted on by the surface tension of a liquid to bring said surfaces inw engagement to close said circuit.

5. An electrical control device for detecting a change in the level of a liquid, said device being located a predetermined distance from the surs face of said liquid, and actuating means in said device comprising two coacting surfaces insulated from each other and relatively movable under the influence of surface tension when the liquid level changes enough so that the surface of the liquid is intersected by said surfaces. y

6. An electrical control device comprising two parts, said parts having surfaces insulated from each other which are separated when the device is immersed in a liquid and which are brought together by the surface tension' of the liquid when they intersect the surface of such liquid, and means for maintaining said surfaces wet with the liquid when they are above the surface of the liquid in order to prevent loss of the surface tension by evaporation of the liquid from said surfaces.

7. An electrical control device comprising a sheet of resilient metallic foil, a body having a surface substantially ooextensive with the surface of said foil, means insulating said body and said foil from each other and for supporting them with said surfaces in spaced relation, a second body having a relatively small surface in contact with said foil, said foil being movable under the influence of the surface tension of a liquid when the device is partially immersed therein to break contact with said second body and make contact with said first body.

8. An electrical control device comprising a rotatable cylinder, a strip of resilient metallic sheet material partly enclosing said cylinder, said strip being normally out of contact with said cylinder but adapted to contact the same when the parts are subjected to the surface tension of a liquid, and a pair of contacts actuated by movement of said strip responsive to rotation of said cylinder when the strip is in contact therewith.

9. An electrical control device comprising a movable surface, a strip of resilient material normally spaced away from said surface but adapted to engage the same when the parts are subjected to the surface tension of a liquid. whereby the movement of said surface is communicated to said strip, and an electrical contact controlled by movement of said strip.

10. An electrical control device comprising two parts at least one of which is a sheet of resilient metal foil, means for insulating said parts from cach other and for supporting them in spaced relation, whereby the sheet of foil is adapted to be pulled into contact with the other part by the surface tension of a liquid when the parts intersect the surface of such liquid.

11. A liquid level indicator comprising a plurality of control devices arranged in superimposed relation in a liquid container, each control device including circuit controlling means actuated by the surface tension of the liquid, an indicator. and circuit connections including said devices and a source of current for controlling said indicator in accordance with the number of said devices which are below the surface of the liquid in the container.

12. A liquid level indicator comprising a plurality of control devices arranged in superimposed relation in a liquid container, each device including circuit controlling means actuated by the surface tension of the liquid, means for maintaining communication between the liquid and all those devices which are above the level thereof so as to subject such devices to surface tension whether they intersect the surface of the liquid or not, an indicator, and circuit connections including said devices and a source of current for controlling said indicator in accordance with the number of said devices which are subjected to the surface tension of the liquid.

13. A device as described in claim 5 wherein one of said two co-acting surfaces is on a movable part formed of magnetic material, and said device includes a coil, the inductance of which changes in accordance with the position oi said movable part.

14. An electrical control device comprising two parts movable with respect to each other and having surfaces acted on by the surface tension of a liquid to bring the surfaces into substantial contact when the surface tension is affected, said parts being normally so positioned that said surfaces are out of contact when not subject to the influences of surface tension, one of said parts being of magnetic material and the other of said parts carrying a coil the inductance of which changes in accordance with the relative position of the two parts.

WALTER KOEPPE. GUSTAV KODAL. 

